This invention relates to a coffee grinder apparatus and more particularly to a coffee grinder apparatus which may be used in combination with a coffee brewer and having a feed worm or auger for feeding the coffee beans from a coffee bean hopper inlet to a set of spring biased grinding burrs.
A typical commercial prior art coffee grinder comprises a hopper for the storage of coffee beans and has an outlet, generally disposed at the bottom of the hopper, communicating with a passageway to a set of grinding burrs. The burrs are generally in the shape of closely positioned disks with facing surfaces provided with meshing teeth or blades that function to grind the beans into ground coffee. A rotatable auger or feed worm is often positioned in the passageway to move the beans from the outlet to the grinding burrs. One of the burrs is generally held stationary while the other burr is rotated on a shaft driven by a grinding motor. Frequently, the feed worm is mounted on the same drive shaft as the rotatable burr for concurrent rotation by the grinding motor.
Most prior art coffee bean grinders of the type described above position the stationary burr of the burr set closer to the grinding motor. The coffee bean outlet communicates with the passageway at a point between the grinding motor and the stationary burr. The feed worm moves the beans away from the motor through an annulus opening in the stationary burr where the beans are then ground and are spun out of the grinder into a container or brew basket for subsequent brewing. Additionally, the spacing between the burrs can be altered by moving a flange supporting the stationary burr axial toward or away from the rotatable burr.
The consistency in grinding depends in part on the concentricity of the burr set. That is, it is desirable that the planes of the burrs are maintained in as parallel relationship as practically possible. Failure to maintain the proper alignment reduces grind consistency. Additionally, the separation of the burr faces plays a role in the quality of the ground coffee. When beans are being fed into the spacing between the burrs, certain types of coffee grounds are not able to clear the burrs fast enough and the burrs begin to jam. Due to friction, ground coffee temperatures may become elevated causing the grounds to burn and flash off some of the flavored oils.
The positioning of the grinding burrs of the prior art described above, however, often creates problems in maintaining the aforementioned grinding consistency and quality of the ground coffee. Because the prior art generally places the rotatable burr at the end of the shaft extending from the motor, the burr faces can become misaligned easily as the positioning magnifies the effect of shaft misalignment, i.e., shaft run out, and bearing end play. Additionally, the burrs cannot accommodate certain types of coffee beans being ground and jamming occurs resulting in flavor distortion as discussed above. To alleviate or minimize this problem, strict attention must be given to closely controlling motor or shaft tolerances, thus adding significantly to the cost of the apparatus.
U.S. Pat. No. 1,989,416 to Hartman describes a grinding apparatus which has a "feeding scroll" that feeds coffee beans from a supply duct to the grinding disks in which the rotatable grinding burr is positioned inwardly of the apparatus with respect to the stationary burr. The rotatable grinding burr of the Hartman patent is driven by a shaft keyed to a worm wheel engaging an actuating worm mounted on the grinder motor drive shaft. Thus the grinding motor is at a right angle to the rotatable burr drive shaft. Additionally, the Hartman patent describes the burrs as being adjustable axially. However, the adjustment is solely done manually through the turning of a ratchet to move the stationary burr to and from the rotatable burr.
It is therefor an object of the present invention to provide for a coffee bean grinding apparatus in which the burrs are self adjusting during the grinding operation.
It is still another object of the present invention to provide for a coffee bean grinding apparatus in which misalignment of the grinding burrs is minimized.
It is still a further object of the present invention to provide for a coffee bean grinding apparatus that positions the grinder closer to the front of the apparatus, permits the grinder motor to directly drive the rotatable grinding burr, and places the rotatable burr close to the grinder motor to reduce misalignment of the burrs.